1. Field of the Invention
The present invention relates to batteries containing metal anodes.
2. Discussion of the Background
Battery manufacturers and users of portable electronic equipment are continuously searching for new high rate, high energy density nonaqueous.sup.1 electrochemical conversion devices that are operable at or near room temperature. In many specialized applications, such as satellites or space vehicles, these devices should also be useful at low temperatures, for example at temperatures of 20.degree. C. below zero. FNT .sup.1 Aqueous electrolytes are incompatible with energetic anode materials and do not function at very low temperatures. Thus they are essentially not used.
Devices that possess these attributes would find use in electronic equipment for space, military, communication and medical applications. Of course, any such device should preferably be inexpensive and facile to manufacture, easily handled, and safe when used.
High rate, high energy density electrochemical cells utilize nonaqueous electrolytes because of their compatibility with energetic metal anodes. The most energetic metal, based on gravimetric coulombic capacity, is aluminum. Unfortunately, available electrolytes that support aluminum electrolysis require elevated temperatures or promote deleterious electrode passivation. Thus, commercially lithium anodes and liquid electrolytes such as thionyl chloride or sulfur dioxide are used.
Unfortunately, lithium metal is much more reactive than aluminum metal, making its handling difficult. The reactivity of lithium metal can result in production problems if proper and expensive precautions are not taken. Lithium anode-based batteries also suffer from other problems. Sulfur dioxide is a volatile material having a boiling point of -10.degree. C. which contributes to handling difficulties and potential safety problems. Lithium-thionyl chloride batteries have been plagued with safety problems that occur when the cells are discharged at high rates. When the cells are short circuited or discharged at high rates, substantial pressures can build up in the cell due to internal heating.
There is therefore a strongly felt need for an alternative nonaqueous electrode/electrolyte combination capable of sustaining high discharge rates and which would not suffer from the above problems.